A flash memory is a type of non-volatile memory. That is, a flash memory is a type of memory that retains stored data without a periodic refresh of electricity. An important feature of a flash memory is that it can be erased in blocks instead of one byte at a time. Each erasable block of memory comprises a plurality of non-volatile memory cells (cells) arranged in rows and columns. Each cell is coupled to a word line, bit line and source line. In particular, a word line is coupled to a control gate of each cell in a row, a bit line is coupled to a drain of each cell in a column and the source line is coupled to a source of each cell in an erasable block. The cells are programmed, read and erased by manipulating the voltages on the word lines, bit lines and source lines.
The voltage level needed to program or erase a non-volatile memory cell can be has high as 12 volts or more. Since an external Vcc power supply to a flash memory is typically 1.8 volts or lower, internal charge pumps are used in the flash memory to provide the required voltage. The internal charge pump is used to boost the external Vcc power supply voltage to a required voltage. Traditionally, charge pumps do not support high current loads, hence the resistive load of the charge pump must be kept at a minimum. Accordingly, charge pump circuits typically incorporate a capacitive voltage divider instead of a resistance voltage divider. For reliable operation of a flash memory, a well regulated charge pump is required. However, typical capacitors used in a voltage divider circuit of an integrated flash memory tend to not be as stable or precise as desired which have a negative effect on the reliability of the charge pump circuit.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a flash memory architecture having a charge pump circuit that incorporates a voltage divider with stable and precise capacitors.